Ivory Coast leader Laurent Gbagbo has barred United Nations aircraft from flying over his country, complicating international efforts to transition power to the U.N. recognized winner of last November's election, Alessane Ouattara.

Ouattara left the Ivory Coast capital on a U.N. helicopter to attend the African Union summit in Ethiopia Thursday. It was the first time he has left the country since the election.

Gbagbo, the incumbent leader, has refused to step down after the U.N. declared his rival the winner of Nov. 28 election.

Since then, the country has spiraled into a violent political standoff, with more than 400 people killed, according to Associated Press reports.

On Tuesday, reports emerged of security opening fire on hundreds of demonstrators celebrating International Woman's day in Treichville. At least four civilians were reported killed. Others were being treated at a nearby hospital for injuries sustained during the attack.

Last week, at least seven women were shot to death by soldiers in armored carriers during a march protesting the entrenched leader.